The proposed research is an investigation of skills in infancy for evaluating perceptually the number of objects in a small array, i.e., three or four objects. This rapid, accurate, perceptual evaluation of small number, called subitizing, is a well-established phenomenon in adults and has been demonstrated in preschool children (Cooper & Starkey, 1977). The course of the development of subitizing and the role it plays in the development of other number skills are both questions of current theoretical dispute. In order to infer that infants are perceiving numerosity, their visual attention to arrays of one numerosity will be habituated and any increase in attention when the numerosity of the arrays is changed will be monitored. During the habituation trials different arrays (of equal numerosity) will be presented so that both the density and the length of the new array to be presented after habituation will have been presented 50% of the time during the habituation trials. These trials will continue until a response decrement of 50% of the maximal fixation response has been reached. When the habituation criterion is met, an array of another numerosity will be presented. Since the length and density of this array matched 50% of the habituation trials, an increase in fixation time to the new array will be used to infer perception of number. Evidence for subitizing in infants would disconfirm the class of theories in which it is proposed that subitizing develops from counting, and would provide support for those theories which propose the converse. Failure to find subitizing in infants in conjunction with successful habituation would not conclusively demonstrate the absence of subitizing, but would lend some support to theories which propose that subitizing develops from counting or from other estimators of gross amount, e.g., a global concept of length.